1. Field of the Invention
This invention relates generally to an electronic camera and, more particularly, to an electronic camera utilizing a charge coupled device (CCD) array as both an image sensing device and a buffer memory.
2. Description of the Prior Art
Still photographic quality electronic cameras require a high resolution image sensing array comprising a substantially higher number of pixels than is required for a standard home television image. This high resolution leads to data transfer problems since the transfer of photographic image data to a digital recording medium cannot be practically completed in a standard television frame of 1/30th of a second. Such electronic cameras generally include a viewfinder comprising a cathode ray tube. The high number of image sensing pixels, however, required to make a photographic quality still print imposes additional memory requirements in order to preview the scene to be photographed through the viewfinder CRT at standard television frame rates with standard television components. Such additional memory requirements are provided by buffer memories which substantially increase the cost, size and power consumption of the electronic camera.
The number of image sensing pixels generally required for an electronic camera to produce a photographic quality still print is in the order of 500,00 to 1 million pixel sensing areas. In order to preview the image to be photographed through the screen of the viewfinder CRT, the image data must be transferred from the image sensing array which generally comprises a charge coupled device (CCD), at an operating frequency in the order of 15 to 30 megahertz in order to operate at a standard television frame transfer rate (30 frames per second). This high rate of video transfer from the image sensing array when digitized generates serial digital data rates in excess of 100 megahertz. Such high frequencies are not practical for the operation of a buffer memory, an image sensing array, or a magnetic disc in a consumer oriented product. In addition, as previously discussed, the amount of image data required to be stored in the frame buffer memory is so large that the cost and size of the buffer memory also becomes prohibitive for a consumer oriented product.
Therefore, it is a primary object of this invention to provide an electronic camera which can provide a photographic quality still print of an image which can be previewed at standard television frame transfer rates without the provision of an additional buffer memory.
It is a further object of this invention to provide an electronic camera which can provide a photographic quality still print of a scene which can be previewed and reviewed from a viewfinder display wherein the image is sensed by a standard CCD array which may be operated in a second mode as a digital buffer memory to allow the imaged scene to be reviewed prior to printing.
It is a further object of this invention to provide an electronic camera for recording still photographic quality prints at a high resolution while allowing for the preview of the scene to be photographed at a low resolution compatible with the standard television frame rate of 1/30th of a second.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.